This research proposal is for a one-year continuation of the study begun in the first two years of my NRSA postdoctoral fellowship. The current study addresses the question of what parameters of grasp are encoded in the simple and complex spike activity of Purkinje cells. My hypothesis is that the simple spike activity of cerebellar Purkinje cells modulates in relation to object volume, shape, and orientation, and to the force generated during the grasp. Object properties appear to be encoded during the reach and early in the grasp of the object and force tends to be encoded late in the grasp. In the current study, the reach component is held constant and the object to be grasped and the force to be generated are varied systematically. The monkey's hand and the object are outside monkey's field of view, removing possible visual contributions to the Purkinje cell discharge. Multiple linear regression analysis will be used to analyze task-related discharge in relation to the force generated and to object properties such as shape, volume and orientation. An additional paradigm I propose is to compare the firing rates of Purkinje cells during the grasp task with and without visual guidance. Two assumption made in both paradigms is that reach is constant and that hand posture will vary with the different objects. The kinematics of the wrist and hand movements will be monitored to test these assumptions. The kinematic data will also be analyzed using singular value decomposition for possible simplifying strategies the CNS may use in the control of grasp. The discharge activity of the population of Purkinje cells will be evaluated using singular value decomposition to identify patterns of activity that may reflect the simplifying strategies observed in the psychophysical studies.